This invention relates to an acridine compound, a photopolymerizable composition using the same as a photopolymerization initiator, a process for producing a resist image and a process for producing a printed circuit board, using the same.
Photopolymerizable compositions comprising an unsaturated monomer or an unsaturated prepolymer and a photopolymerization initiator are known to be polymerized by irradiation of light. These photopolymerizable compositions are used in a variety of fields such as printing plates for lithography, letterpress printing, intaglio printing, etc., photocurable inks, coating compositions, printed circuit substrates, adhesives, etc.
As the photopolymerization initiator, there have been proposed various compounds such as benzophenones, benzoins and the like aromatic ketones. But, these aromatic ketones have defects in that obtained polymers are colored and light irradiation for a long period of time is necessary due to their small effects. Thus, these aromatic ketones are unsatisfactory in practical use.
On the other hand, in order to increase light sensitivity, there are disclosed a combination of an aromatic ketone such as aminophenyl ketone and 2,4,5-triarylimidazole dimer (U.S. Ser. No. 731,733, Japanese Patent Examined Publication No. 48-38403), a combination of aminophenyl ketone and an active methylene compound or an amino compound (U.S. Serial No. 877,853, Japanese Patent Examined Publication No. 49-11936), an acridine or phenazine capable of including a fused benzol ring (Japanese Patent Examined Publication No. 53-27605), a 9-substituted acridine compound (Japanese Patent Unexamined Publication No. 47-4126), a combination of 9-phenylacridine and a thiol group-containing heterocyclic compound (Japanese Patent Unexamined Publication No. 59-226002), a substituted 9-benzoylacridine (Japanese Patent Unexamined Publication No. 60-164739), etc. But these compounds are insufficient to provide light sensitive photopolymerizable compositions.